The need to position an article rapidly and accurately with respect to an operative tool is a basic requirement in much of today's automated machinery. The approaches which have been taken to accomplish this end have varied depending on the type of operative tool involved and the type of article which is to be positioned. For instance, in automated sewing the operative tool is usually a cyclically operated sewing needle which moves into and out of an article that is positioned thereunder. The article may be either a number of separate pieces of material that are to be joined together or a separate piece of material requiring a decorative pattern. In any event, the article is positioned relative to the sewing needle by a positioning apparatus. This apparatus preferably moves the article only during that portion of the sewing cycle when the needle is withdrawn from the material. This places some rather stringent timing requirements on the positioning apparatus for high speed sewing. These stringent timing requirements usually include the need to quickly change the direction in which the article is being fed underneath the needle. This latter requirement is usually met by implementing two separate directional motions which combine to define any particularly desired feed direction for the next stitch. For instance, separate motions in an X and Y direction within a cartesian coordinate system will accomplish such a feed direction capability. These separate motions are commonly referred to as occurring with respect to X and Y axes.
The need to simultaneously implement motion along two separate axes at relatively high speed has resulted in various types of positioning apparatus. These have included mechanisms which superimpose the motion occurring along one axis with respect to the motion occurring along the second axis. These mechanisms have by their very nature often been quite complex. These mechanisms have moreover sometimes introduced undesirable vibrations into the overall positioning of the article relative to the sewing needle.
It is to be appreciated that while certain drawbacks have been herein discussed relative to positioning apparatus for sewing machines, the same considerations are also equally applicable to certain other automatic machinery. To this extent, the invention which will be hereinafter described is also broadly applicable to automatic machinery in general.